[Hyperplastic polyposis syndrome: phenotypic diversity and association to colorectal cancer]

Hyperplastic polyposis syndrome (HPS) is an uncommon disorder characterized by hyperplastic polyps (HP) occasionally associated with serrated adenomas (SA) or mixed polyps (MP) and defined by clinical criteria (OMS/Cleveland). HPS is heterogeneous regarding the number and size of polyps, and it is associated with colorectal cáncer (CRC) and a family history. Its genetic basis is unknow. We describe individuals with HPS criteria from a series of families assessed in our Unit of Genetic Advice for colonic polyposis. Our objective is to identify the clinical characteristics of this syndrome.Retrospective study of 197 families with colonic polyposis (1998-2011), identifying patients with HPS criteria. To know the number of polyps, we took into account polypectomies and/or the histologic study of surgical samples. Polyps were classified into adenomas, serrated lesiones (HP and SA) and MP. Genetic studies revealed: microsatellite instability (MSI), MUTYH gene variants (p.Tyr165Cys, p.Gly382Asp and p.Glu396GlyfsX43) and APC gene.Eighteen individuals, with a median age of 51.1 years, had criteria of HPS (11M/7F). Number of HP varied between 14 and 100 coexisting with classical adenomas, SA and MP in 14 individuals (77.8%). Localization of polyps: ascending and descending colon in 13 individuals (72.2%) and only descending colon in 5 (27.8%). A CRC was detected in 10/18 (55.6%) patients, and 3 of them had a double CRC, a family history in 3 patients (16.7%) and a history of HPS in one. IMS was not detected in 8 CRC nor in 3 adenomas studied; we detected 2/13 heterozygous mutations in the MUTYH gene (p.Gly382Asp) and one variant with an unknown biological significance in the APC gene (p.Ser926Pro).The phenotypic variability of HPS difficults its identification, hence it is important to adhere to the clinical criteria established for its classification as well as to establish screening guidelines for CRC on the basis of its high incidence.